Method for producing fiber-reinforced resin golf club shaft

ABSTRACT

A production method of a golf club shaft made of a fiber-reinforced resin according to the present invention comprises the steps of driving and rotating a shaft substrate made of an uncured fiber-reinforced resin on the axis thereof, moving a plurality of creel stands in parallel in the axial direction of the shaft substrate, and feeding out tapes from a plurality of the creel stands and winding and laminating the tapes simultaneously and spirally on the outermost layer of the shaft substrate for integrally molding them while the rotating speed of the shaft substrate and the moving speed of the creel stands are being controlled simultaneously. An apparatus for producing a fiber-reinforced resin golf club shaft according to the present invention comprises a support shaft for supporting a cylindrical shaft substrate molded from an uncured fiber-reinforced resin, a driving motor for driving and rotating the support shaft, a feed screw disposed in parallel with the support shaft, another driving motor for driving and rotating the feed screw, different from the driving motor, a plurality of nuts meshing with the feed screw, creel stands for tapes made of organic polymers, supported by the nuts, respectively, still another driving motor for driving and rotating a part of a plurality of the nuts, different from the two driving motors, and a controller for controlling the rotating speed of each of the driving motors.

BACKGROUND OF THE INVENTION

This invention relates to a method of, and an apparatus for, producing afiber-reinforced resin golf club shaft. More particularly, thisinvention relates to a method of, and an apparatus, for producing afiber-reinforced resin golf club shaft which can carry out continuouslyand simultaneously and in one process step an operation of winding atape made of an organic polymer on the full length of a shaft substrateand an operation of winding a tape on only a part of the shaftsubstrate.

When the shaft weight of golf club shafts in general is reduced for thesame shaft length, a moment using a certain point in the proximity of agrip portion as a support point (or a swing balance) becomes small.Therefore, head speed and controllability of a ball's orbit can beimproved, flying distance can be increased and directionality can bestabilized. When the shaft weight is decreased for the same swingbalance, the club length can be increased and the head weight can beincreased, as well. Therefore, an increase in the flying distance can beexpected.

However, when the shaft weight is decreased, its strength becomesinsufficient. To supplement this insufficiency, partial reinforcement ofthe shaft must be made. Greater reinforcement is necessary particularlyfor the tip side (the fitting side of the shaft to the head) whichreceives the greatest impact force when a ball is hit by the club head.In the case of fiber-reinforced resin golf club shafts, for example, thenumber of laminate layers of a fiber-reinforced resin sheet is increasedon the tip side when the shaft is made.

When the reinforcement structure described above is employed, however,the centroid position of the shaft shifts towards the tip side.Therefore, even when the shaft weight is decreased, the swing balance ofthe shaft can be hardly reduced. Further, the effect of an increase ofthe head weight and the effect of an increase of the shaft length cannotbe expected, either, at the same swing balance by merely reducing thetotal weight.

An inventors of the present invention previously filed patentapplication Ser. No. 08/533,748 (now U.S. Pat. No. 5,634,861) for ashaft having the structure of a fiber-reinforced resin golf club shaftwhich solves the problems described above. In this golf club shaft, atape made of an organic polymer is wound only on the distal end portionof the shaft by varying a winding pitch.

When such a fiber-reinforced resin golf club shaft is molded, shaperetention of an uncured fiber-reinforced resin, discharge of anexcessive resin and volume compression of air are carried out at thetime of molding of the shaft. Therefore, a tape wrapping step of windinga heat-shrinkable polymer having good mold releasability on the fulllength of the shaft is necessary.

According to the prior art method, however, at least two steps, that is,a step of wrapping the tape at the distal end portion and the step ofwrapping the tape on the shaft throughout its full length, arenecessary, and there remains the problem that the work efficiency andproductivity are extremely low.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method of, andapparatus for, producing a fiber-reinforced resin gold club shaft whichcan wind continuously and simultaneously two kinds of tapes in oneprocess step when the tapes are wound on a shaft substrate made of afiber-reinforced resin.

It is another object of the present invention to provide a method of,and an apparatus for, producing a fiber-reinforced resin golf club shaftwhich can wind at least one of two kinds of tapes at variable pitches.

To accomplish the object described above, the present invention providesa method for producing a golf club shaft made of a fiber-reinforcedresin which comprises the steps of rotating a shaft substrate made of anuncured fiber-reinforced resin about an axis thereof, moving a pluralityof creel stands in parallel in the axial direction of the shaftsubstrate, feeding out tapes from a plurality of the creel stands, andwinding and laminating the tapes simultaneously and spirally on theoutermost layer of the shaft substrate for integrally molding them whilethe rotating speed of the shaft substrate and the moving speed of thecreel stands are being controlled simultaneously.

When a golf club shaft is produced by such a method, two kinds of tapescan be wound continuously and simultaneously in one process step.According to the method described above, the winding pitch of the tapescan be varied by controlling the moving speed of the creel stands.Therefore, the winding can be carried out efficiently without thenecessity for resetting and exchanging the creel stands that have beennecessary in the past.

In the present invention, a reinforcing tape made of an organic polymerand a shape-retaining tape made of a heat-shrinkable polymer arepreferably used as the plurality of tapes described above. Thecombination of such tapes makes it possible to simultaneously carry outthe winding step of the tape constituting a reinforcement layer and thewinding step of the shape-retaining tape. In this case, the reinforcingtape needs be wound in only the distal end region of the shaft substratewhich requires reinforcement, while the shape-retaining tape may bewound on the, shaft substrate throughout its full length. When themoving speed of the creel stand for the reinforcing tape is graduallydecreased from the rear end side of the shaft substrate towards itsdistal end, the thickness of the reinforcement layer can be made smalleron the rear end side of the shaft substrate and greater on the distalend side.

On the other hand, a production apparatus for producing afiber-reinforced resin golf club shaft according to the presentinvention for accomplishing the objects described above comprises asupport shaft for supporting a cylindrical shaft substrate molded froman uncured fiber-reinforced resin, a driving motor for driving androtating the support shaft, a feed screw disposed in parallel with thesupport shaft, another driving motor for driving and rotating the feedscrew, which motor is different from the driving motor described above,a plurality of nuts meshing with the feed screw, creel stands for tapesmade of organic polymers, supported by the nuts, respectively, stillanother driving motor for driving and rotating a part of a plurality ofthe nuts, which driving motor is different from the two driving motorsdescribed above, and a controller for controlling the rotating speed ofeach of the driving motors. In this case, it is preferred that the twonuts are provided, one of the nuts supports the creel stand for ashape-retaining tape made of a heat-shrinkable organic polymer, theother nut supports the creel stand for a reinforcing tape made of anorganic polymer having high strength and high elastic modulus, and thenut supporting the reinforcing tape is driven and rotated by the drivingmotor.

Further, a production apparatus of a fiber-reinforced resin golf clubshaft according to the present invention comprises a support shaft forsupporting a cylindrical shaft substrate molded from an uncuredfiber-reinforced resin, a driving motor for driving and rotating thesupport shaft, a plurality of feed screws disposed in parallel with thesupport shaft, a plurality of driving motors for individually drivingand rotating a plurality of feed screws, each being different from thedriving motor described above, a plurality of nuts each meshing witheach of a plurality of the feed screws, a plurality of creel stands fortapes made of organic polymers, supported by a plurality of the nuts,respectively, and a controller for controlling the rotating speed ofeach of the driving motors. In this case, it is preferred that two feedscrews are provided, the nut meshing with one of the feed screwssupports the creel stand for a shape-retaining tape made of aheat-shrinkable organic polymer, and the nut meshing with the other ofthe feed screws supports the creel stand for a reinforcing tape made ofan organic polymer having high strength and high elastic modulus.

According to the production apparatus for producing a fiber-reinforcedresin golf club shaft described above, the production method of thepresent invention can be practised by suitably controlling each drivingmotor by the controller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural view of an apparatus for producing agolf club shaft according to a first embodiment of the presentinvention;

FIG. 2 is an schematic structural view of a apparatus for producing agolf club shaft according to a second embodiment of the presentinvention;

FIG. 3 is an explanatory view showing a relative rotating speed of a nutto a feed screw;

FIG. 4 is a front view of a golf club shaft made of a fiber-reinforcedresin produced by a winding apparatus according to the first embodimentof the present invention; and

FIG. 5 is a partial enlarged sectional view showing the state where atape is wound and laminated on a part of a shaft substrate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First of all, a golf club shaft produced by the present invention willbe explained. As shown in FIGS. 4 and 5, a cylindrical shaft substrate 1is constituted by laminating a sheet-like prepreg impregnated with anuncured resin. Fiber-reinforced resin sheets of a carbon fiber, a boronfiber, a glass fiber, an aramide fiber, an alumina fiber, a siliconcarbide fiber, a tirano fiber, an amorphous fiber, etc, are used forthis shaft substrate 1. A reinforcing tape 3a made of an organic polymerhaving a high strength and a high elastic modulus such as an aramide iswound and laminated on a reinforcement zone L in a distal end area onthe tip side X of the shaft substrate 1 as an integral unit. Ashape-retaining tape 3b made of a thermo-shrinkable organic polymer suchas a polyester or a polypropylene is then wound on the outside of theuncured shaft substrate 1 and reinforcing tape 3a. This shape-retainingtape 3b is peeled off after a curing treatment.

In order to achieve effective reinforcement without increasing theweight, the reinforcement zone L of the reinforcing tape 3a is set so asto start at the tip end and to end up at a point having a distance of150 to 500 mm when the tip end of the shaft substrate 1 is set to 0. Thethickness t₂ of this reinforcing tape 3a is not greater than 0.05 mm ata point 50 mm towards the tip side from a point closest to the butt sideY of the reinforcement zone L, and the thickness t₁ of the reinforcementlayer made from the reinforcing tape 3a is at least 0.1 mm in the zonefrom the tip end to a point 50 mm from the tip end of the reinforcementzone L.

FIG. 1 is a schematic structural view of a an apparatus according to thefirst embodiment of the present invention. In this drawing, thecylindrical shaft substrate 1 made of the uncured fiber-reinforced resinis shown supported by a support shaft 7. This support shaft 7 is drivenfor rotation by a driving motor M1. A feed screw 2 is disposed inparallel with the support shaft 7 and is driven for rotation by adriving motor M2. Threaded nuts 6a and 6b mesh with the feed screw 2 andsupport creel stands 4a and 4b, respectively. A reinforcing tape 3a anda shape-retaining tape 3b each made of an organic polymer are wound onthe creel stands 4a and 4b, respectively, and the tapes 3a and 3b arefed in accordance with the revolution of the shaft substrate 1. The nut6a for supporting the creel stand 4a of the reinforcing tape 3a isrotated by still another driving motor M3 relative to the feed screw 2.The rotating speeds of these driving motors M1, M2, and M3 arecontrolled by a controller 5. In other words, the driving motor M1 forthe support shaft 7 and the driving motor M2 for the feed screw 2 are socontrolled as to always rotate synchronously at a constant ratio, andcontrol is made by changing the ratio of the rotating speed of thedriving motor M2 for the feed screw 2 to the rotating speed of thedriving motor M3 for the nut 6a.

When, for example, the reinforcing tape 3a is wound at a variable pitcharound the shaft substrate 1, the control calculation system by thecontroller 5 described above can be executed in the following way.

FIG. 3 shows the relationship between the time passed T from the shaftof winding and the relative rotating speed N of the nut 6a to the feedscrew 2. Incidentally, symbol t represents a set time from the shafttill the end of winding (cycle). In FIG. 3, when the relative rotatingspeed N deceases, the winding pitch of the reinforcing tape 3adecreases, too. On the other hand, the winding pitch of theshape-retaining tape 3b remains constant. At this time, assuming thatthe lead of the feed screw 2 is P and the relative rotating speeds ofthe nut 6a at the start and the end of winding are N₁ and N₂,respectively, the relative rotating speed N of the nut 6a and its movingdistance L can be expressed as follows: ##EQU1## From (2),

    t=120L/P(N.sub.1 +N.sub.2)                                 (3)

From (1)+(3),

    N=(N.sub.2 -N.sub.1)(N.sub.2 +N.sub.1)TP/120L+N.sub.1      (4)

Assuming that the actual rotating speeds of the nut 6a at the relativerotating speeds N, N₁ and N₂ of the nut 6a to the feed screw 2 areN_(N), N_(N1) and N_(N2) and the rotating speed (constant) of the feedscrew 2 is N_(B), the relations N=N_(N) +N_(B), N₂ =N_(N2) +N_(B) and N₁=N_(N1) +N_(B) are established. Therefore, when these relations aresubstituted for (4), the actual rotating speed N_(N) of the nut 6a canbe expressed as follows:

    N.sub.N =(N.sub.N2 -N.sub.N1)(N.sub.N1 +N.sub.N2 +2N.sub.B)TP/120L+N.sub.N1(5)

In the equation (5) given above, the moving distance L of the nut 6a andits rotating speeds N_(N1) and N_(N2) are inputted from digital switchesof an operation board so that the controller 5 can calculate theequation (5) at a predetermined time interval and inputs each resultN_(N) to the driving motor M₃. Incidentally, it is also possible toinput the winding pitch of the reinforcing tape 3a and to convert thepitches to the rotating speed of the nut 6a in place of the rotatingspeeds N_(N1) and N_(N2) of the nut 6a.

Next, a method for producing a shaft for fiber-reinforced resin golfclub by the apparatus described above will be explained.

First, the starting points of the reinforcing tape 3a and theshape-retaining tape 3b on the shaft substrate 1 are set and then theshaft substrate 1 is rotated about its axis and at the same time, thecreel stands 4a and 4b are moved in parallel in the axial direction ofthe shaft substrate 1. While the rotating speed of the shaft substrate 1and the moving speed of the creel stands 4a and 4b are simultaneouslycontrolled by controlling the rotating speeds of the driving motors M₁,M₂ and M₃ by the controller 5, the tapes 3a and 3b are fed out from thecreel stands 4a and 4b, respectively. In this way, the reinforcing tape3a and the shape-retaining tape 3b are wound and laminated spirally andsimultaneously on the outermost layer of the shaft substrate 1.

When the golf club shaft is produced by such a method, two kinds oftapes, i.e., a reinforcing tape 3a and a shape-retaining tape 3b, can bewound continuously and simultaneously in one step.

When a golf club shaft having partially different thickness in thereinforcing layer thereof is to be made by using the apparatus describedabove, the thickness of the reinforcing layer can be made small at therear end of the shaft substrate 1, and greater, at the distal end bygradually decreasing the moving speed of the creel stand 4a for thereinforcing tape 3a from the rear end side of the shaft substrate 1towards its distal end. The winding pitch of the reinforcing tape 3a ischanged in accordance with the thickness and width of the tape 3a, itswinding length and with the taper angle of the shaft substrate 1 beforewinding. When, for example, the taper angle of the shaft substrate 1 is6/1,000 to 15/1,000 for a reinforcing tape 3a having a thickness of 16μand a width of 15 mm that has been conventionally used, the windingpitch must be continuously changed between 4.8 and 2.4 mm for a windinglength of 500 mm. When the thickness of the reinforcing tape 3a is 10μ,the winding pitch must be continuously changed between 3.5 and 1.5 mm,and when the thickness is 25μ, the winding pitch must be continuouslychanged between 9 and 3.75 mm.

To prevent the uncured fiber-reinforced resin layer from being twistedby the tension of the tape when the reinforcing tape 3a is being woundon it, winding of both the reinforcing tape 3a and the shape-retainingtape 3b is preferably carried out substantially simultaneously with eachother. The first embodiment of the present invention makes it possibleto conduct this simultaneous winding by moving the creel stand 4a forthe reinforcing tape 3a and the creel stand 4b for the shape-retainingtape along the feed screw 2 under control of the controller 5.

In the present invention, the elastic modulus of the reinforcing tape 3ais higher than that of heat-shrinkable films such as polyester,polypropylene, etc, which are used as a wrapping tape, at the time ofnormal molding. Therefore, when a reinforcing tape 3a made of theorganic polymer is partially used for the shaft substrate 1, a tensionof at least 45 Newtons (when thickness is 16μ and width is 15 mm) isnecessary so that the tape can be wound and laminated on the taper-likeshaft in close contact therewith without generating creases. Further,this tension must be changed in accordance with the change of thethickness and the width of the reinforcing tape 3a.

When the tension is smaller than 45 Newtons, elongation is so small thatthe film is likely to crease and air is likely to be entrapped betweenthe tape-like films. In consequence, a drop in strength occurs andappearance is deteriorated, as well. On the other hand, when the tensionbecomes excessive and beyond 90 Newtons, or when the fastening forcebecomes too great as the film is tightly wound in superposition, aditch-like step is likely to occur at the boundary of the reinforcementzone due to the influences of thermal shrinkage or disturbance is likelyto occur in the orientation of the fiber. Therefore, stressconcentration locally occurs and the strength of this portion is likelyto drop.

FIG. 2 shows a second embodiment of the winding apparatus. In thisdrawing, the feed screws 2a and 2b are shown disposed in parallel withthe support shaft 7, and are individually driven for rotation by thedriving motors M₃ and M₂, respectively. The nuts 6a and 6b mesh with thefeed screws 2a and 2b, respectively, and support the creel stands 4a and4b, respectively. The reinforcing tape 3a and the shape-retaining tape3b are wound on the creel stands 4a and 4b, respectively. The rotatingspeeds of the driving motors M₁, M₂ and M₃ are controlled by thecontroller 5.

When the tapes 3a and 3b are wound continuously on the shaft substrate 1or when the winding pitch is changed or when the tapes are wound only ona part of the shaft substrate 1 by using the apparatus according to thisembodiment, the operations are carried out in the same way as in thefirst embodiment. In other words, the tapes 3a and 3b are fed out fromthe creel stands 4a and 4b held on the feed screws 2a and 2b,respectively, to the shaft main body 1 which is driven for rotation, andwhile the rotating speed of the shaft substrate 1 and the rotating speedof the feed screws 2a and 2b are simultaneously controlled by thecontroller 5, a plurality of tapes 3a and 3b are simultaneously woundand laminated. Incidentally, the other construction and function are thesame as those of the first embodiment. Therefore, like referencenumerals are put to like constituents, and the explanation will beomitted.

As described above, the present invention can wind continuously andsimultaneously two kinds of tapes in one step and can moreover changethe winding pitch of the tape. Therefore, because the winding operationcan be carried out efficiently without the need for resetting or forexchanging the creel stands, the present invention can improve theworking efficiency and productivity.

What is claimed is:
 1. A method for producing a golf club shaft made ofa fiber-reinforced resin, comprising the steps of:rotating a shaftsubstrate made of an uncured fiber-reinforced resin about a longitudinalaxis thereof; moving a first creel stand containing a reinforcing tapemade of an inorganic polymer in a direction parallel to the axis of saidrotating shaft substrate; moving a second creel stand containing ashape-retaining tape made of a heat shrinkable polymer in a directionparallel to the axis of said rotating shaft substrate; feeding out saidtapes from said moving creel stands and winding and laminating saidtapes simultaneously and spirally on an outermost layer of said rotatingshaft substrate; and simultaneously and independently controlling arotating speed of said shaft substrate and a moving speed of said creelstands so that said reinforcing tape is wound only on a part of saidshaft substrate and said shape-retaining tape is wound on a full lengthof said shaft substrate and so that independent of the rotating speed ofthe shaft substrate and independent of the moving speed of the secondcreel stand, the moving speed of said first creel stand for saidreinforcing tape gradually decreases in a direction toward a distal endof the shaft substrate in a distal end region that extends between aposition spaced from said distal end and said distal end of said shaftsubstrate, whereby the thickness of a layer of said reinforcing tapebeing wound on said shaft becomes gradually thicker in a directiontoward the distal end thereof from said position spaced from said distalend.
 2. The method for producing a fiber-reinforced resin golf clubshaft according to claim 1, wherein the reinforcing tape is wound on therotating shaft substrate at a tension of at least 45 Newtons.